This paper presents an updated catalogue of the freshwater invertebrates of the Azores archipelago and reviews the published records to account for the current taxonomic status and changes in the nomenclature of the listed taxa. The number of freshwater invertebrate species that has been recorded in the Azores has risen sharply throughout the 20th century to 241 species based on field collections and the identification by several generations of local and foreign researchers. The freshwater fauna has been described as the following: (i) being “disharmonic”, i. e. , lacking taxa commonly found in continental freshwater systems such as the Plecoptera, and (ii) possessing a relatively high degree of endemism in selected groups. As expected, most recorded invertebrates are primarily of Palaearctic origin. However, endemic species make up 11 % of the freshwater invertebrate fauna, which emphasises the unique character of Azorean freshwater habitats, the importance of conservation measures and the need to continue the study of these systems.